I am looking for articles with PFM implementation of voltage converters (Buck or Boost). In particular the dynamic behaviour of the system using PFM over Pulse Frequency Modulation (PWM).
Hi Mr.Dixon,
You can refer to this article for understanding the basic concepts of PWM and PFM.
http://www.digikey.com/en/articles/techzone/2014/mar/the-advantages-of-pulse-frequency-modulation-for-dc-dc-switching-voltage-converters
In general, PFM is good for energy-efficiency at light load conditions and dynamic response of the system towards changes in load. However, it increases the complexity of control and also results in unwanted EMI if the switching frequency is too high. A combination of both PWM and PFM is typically the state of the art, which combines advantages of both techniques.
A commercially available controller that employs both PWM and PFM control techniques is
https://www.fujitsu.com/downloads/EDG/binary/pdf/find/25-5e/7.pdf
http://www.ti.com/lit/ds/symlink/tps61086.pdf
http://www.onsemi.com/PowerSolutions/product.do?id=NCP1523
I hope this answers your question. Feel free to message me when you need further clarifications.
Thanks for replying Swaminathan Narayanaswamy....
Thank you for the report links. I have already all the above report links. Digikey is reporting on what they conclude is a fact, which is not. Fujitsu, TI and ONSEMI report ed on lab findings based on what they have developed behind closed doors. These reports show no dynamic analysis based on the equivalent circuit modelling and the converter operational regime. What is the system operational range? How the PFM is modelled? PWM modelling is well know to power converter developers and engineers. This is due the fact that the Newton-Raphson roots finding method can be easily applied over the system operational regime. But finding the roots of PFM and it's operational regime is a scenario by itself.
Question!
What is considered light load (the range)?
Yes! EMI is an issue in PWM and PFM. What operational regime this would be? The only complexity of the PFM control system, that is, what duty cycle the pulse should have in other for the inductor to store maximum electromagnetic energy for the load.
Therefore, research and scientific articles are lacking in this area. The industrial reports from big companies cannot be considered as facts based on my findings, conclusion and opinion of power converters technology.
I hope it will be useful.
S.
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